Amsoil Saber specific question: Added too much and piston seized again!

Discussion in '2-Stroke Engines' started by Fletch, May 9, 2011.

  1. Fletch

    Fletch Member

    This is the second time I've done this and I want to kick myself!! I had just rebuild the top end too :veryangry:

    It's my fault though so I can't blame the engine.

    My question:

    When my piston seized the first time it happened right after I refilled and changed the mix from 60:1 to 40:1.

    This time I was running 50:1 and I'm not sure exactly what the new mix was because I added it to the tank at the pump. The tank filled before I could get to my pre-calculated intended amount of gas, so I had to estimate it.

    What I am wondering is if I was running a richer mix to begin with (say 70:1 for example) and then I changed to 60:1 or 50:1... would the same thing happen? Or is it maybe a situation where if I run 40:1 or more it will seize (meaning oil specific)? Is it just the relative amount of change in the oil at any ratio, or the fact that I hit some kind of "magic number" at 40:1?

    I hope that makes sense, and I know it is purely speculation but I'd appreciate any opinions. My Mikuni carb is very sensitive to changes because it is so fine-tuneable (not a real word). For some reason I think the tolerance on an NT would be higher (more forgiving).


  2. RdKryton

    RdKryton Active Member

    I can't see how going to a richer oil mixture would cause it to seize. If you were going the other way I could see it but not richer. The only thing I can think of is 40:1 is still too lean for a fresh rebuild. Everything I have read calls for almost twice as much oil than you are using until the engine is broken in.

  3. Fletch

    Fletch Member

    More oil= less gas, so it runs too lean. It has happened to me twice now immediately after switching ratios mid ride. I was on a 100 mile round trip ride and the engine was running flawlessly. Messed up my calculation on how much oil to add to the tank and seized about 1 mile later. Last time the exact same thing. Saber is a "100:1" oil, and the Amsoil guys recommend 50:1 for these engines. That probably equates to 25:1 or so of a "regular" 50:1 synthetic. last time this happened Pablo agreed that 60:1 of Saber was plenty of lubrication.
    Last edited: May 9, 2011
  4. RdKryton

    RdKryton Active Member

    More oil is just more oil. You still have the same amount of fuel gas mixture going into the engine unless you changed the jets or needle setting. Even though the amount of gas is less, the oil is more and that should make up for it with more lubrication and cooling. I still believe the oil mixture not the fuel mixture is too lean.
    I know you younger guys believe in the 100:1 oils but I am old school and think you are walking a thin line between an engine running like a raped ape and a paper weight. It's just my opinion and it's only worth as much as you paid for it. lol Best of luck and I hope it all works out for you!

  5. RdKryton

    RdKryton Active Member

    Just my thoughts

    Hi again Fletch
    I hope I didn't make you mad at me or the forum with my comments. I am not familiar with the 100:1 oils that's why I gave my "opinion" and did not offer it up as fact. If I did that was not my intention. All the 2-stroke experience I have is with older stuff where even 50:1 would cause a motor to seize up! I hope you do get it worked out.
    I just had another thought, (oh no) that maybe the tolerances were just too tight so no matter what oil you used it would seize up anyway.
    Well I hope your up and running soon.

  6. Fletch

    Fletch Member

    No not at all.. I appreciate different views. If it didn't happen to my twice under identical circumstances I'd be inclined to agree with you, but I can't deny my experience. My mikuni carb needs to be finely tuned so I think a more basic carb without a pilot circuit would handle it. I don't know what you mean by tolerances though?

    I rode 50 miles without a hitch. Spent the night, and road 30 miles to the gas station on a bike with 200 miles on it, where I filled up and changed the ratio. A mile down the road I seized up. Same thing happened a mile down the road when I refilled with more oil last time. I could definitely run more oil, but I need to increase the jet size for that. My engines have both been ported with expansion chambers, so they rev like crazy and I never really need to go beyond 1/2 throttle.
  7. spad4me

    spad4me Member

    The number one killer of air cooled two stroke engine's is stopping when the engine is hot and also stopping the airflow over the cooling fins.

    The porting and chamber make more heat as well as more power.
    I only use a Castor synthetic oil mix.
    The Castor ash is still a a lube. The synthetic dilutes the castor so it does not carbon up.

    Try a castor based oil.


    I run a gp460 in 120 degree heat as well as happytimes .
    I never stop never.
    Do not use engine braking down hill .
    There is no oil when you do this.
  8. RdKryton

    RdKryton Active Member

    Oh no! Another thought.
    Your problem happened right after you fueled up both times. It might be temperature related. Maybe the cold fuel didn't react well with the very hot engine and the metals contracted at different rates causing the engine to seize. That would explain having the same problem even with the different oil ratios. Maybe you just need to let the engine to cool all the way down before riding off or ad fuel to the tank before it is almost empty. That way the fuel will not be as cold and the engine not as hot. Once again these are just my thoughts. Take them for what they are worth.

    Last edited: May 10, 2011
  9. Fletch

    Fletch Member


    That's an excellent theory, but I had a decent amount of fuel in my tank this last time, and wasn't completely empty the time before either. The time before I had the fuel with me in my bike bag, so it was warm. I really think it's the oil because that was the obvious changing variable both times. Maybe I was just tuned to the edge of too lean, and the added oil put it over the edge. Again... I think the Mikuni carb or carbs in general have different reactions to changes. I think it was Gearnut that told me that racers will experiment with leaning the bike out with adding oil, but only when they have an extra bike on hand. Because the NT that most people use only has a main jet, I think it has a much wider tolerance than a finely tunable carb. That's my theory is that it is the combo of the specific carb and oil mix.

    BTW, Many people stopped using the CNS because it ran too lean. I think the same situation was going on there. they didn't have the replacement jets and/or know-how to tune it correctly, so the stock settings were lean to begin with. Plus different oil mixes (some people as high as 16:1!!) will obviously affect the air/fuel mix. The pilot circuit affects the whole throttle range somewhat, so if it's too lean it can really lean out the slide and main jet range.
    Last edited: May 15, 2011